1. Field of the Invention
The present invention relates to a machine for attachment of a cover to a book block and a book binding apparatus having the same.
2. Description of the Related Art
As one of book binding processes, there is a cover attachment process of applying a cover to a book block. In this process, a machine for attachment of a cover to a book block is used. The machine includes a vertically movable press plate, and a pair of nip plates arranged on an upper surface of the press plate. The book block is held above the pair of nip plates in a manner such that a back surface of the book block is opposed to a gap between the pair of nip plates. When the press plate moves upward, the cover is pressed against the back surface of the book block to which glue is applied, the book block and the cover are nipped between the pair of nip plates, and the cover is pressed against both sides of a lower end of the book block, so that the cover is attached to the book block.
In this case, when the cover is attached to the book block in a way that the cover is folded at a right angle along a corner of the back surface of the book block, an excellent finished book with a beautiful appearance can be obtained.
However, in the case of a thin book block, a small amount of glue applied to a back surface of the book block. Therefore, if a height of the press plate when the cover is attached to the book block is excessively low, the glue is not sufficiently supplied to both sides of the back surface of the book block. As a result, the cover is rounded at corners of both sides of the back surface of the book block, and the processing quality of the cover attachment becomes poor. In the case of a thick book block, a large amount of glue applied to a back surface of the book block. Therefore, if the height of the press plate when the cover is attached to the book block is excessively high, the glue sticks out toward both sides of the book block, the cover swells at both sides of the back surface of the book block, and the processing quality of the cover attachment becomes poor.
In other words, in order to obtain good processing quality of the cover attachment, it is necessary to adjust the height of the press plate of the machine when the cover is attached to the book block depending on a thickness of the book block.
A machine for attachment of a cover to a book block having the function of adjusting the height of a press plate when a cover is attached to a book block is known as a conventional technique. FIG. 8 is a side view showing an outline structure of the conventional machine for attachment of a cover to a book block.
As shown in FIG. 8, the conventional machine for attachment of a cover to a book block includes a block 50 mounted in a frame (not shown) and guided for vertical movement. A press plate 51 is attached to an upper surface of the block 50. A pair of nip plates 52a and 52b is arranged on an upper surface of the press plate 51. A cover is placed on the press plate 51 and the pair of nip plates 52a and 52b. A rod 53 projects from a lower surface of the block 50.
The machine further includes a lever 55 mounted in the frame so as to swing around a center shaft 54. A first roller 56a is attached to a tip end of one arm (55a) of the lever 55, and a lower end of the rod 53 abuts against the first roller 56a from above. The machine also includes a first sprocket 58 and a cam 59 which are attached to a rotation shaft 57 mounted in the frame. The cam 59 abuts, from above, against a second roller 56b attached to a tip end of the other arm 55b of the lever 55.
The machine further includes a first motor 60 and a second sprocket 61 mounted on a drive shaft 60a of the first motor 60. An endless chain 62 is extended between the first and second sprockets 58 and 61. When the first motor 60 is driven, the cam 59 rotates, and thereby the lever 55 swings. When the lever 55 swings, the rod 53 vertically reciprocates, and thereby the block 50 vertically reciprocates.
The machine also includes a clamp unit (not shown). The clamp unit is mounted in the frame for clamping a book block at both sides thereof in a way that a back surface of the book block is directed downward. Glue is previously applied to the back surface of the book block. The clamp unit arranges the book block above a gap of the pair of nip plates 52a and 52b in a manner such that the back surface of the book block faces the gap.
As the block 50 moves upward, the press plate 51 moves upward together with the pair of nip plates 52a and 52b. After the cover is pressed against the back surface of the book block, the pair of nip plates 52a and 52b clamps a lower end of the book block at both sides thereof, the cover is pressed against side surfaces of the lower end of the book block, and thereby the cover is attached to the book block.
In addition, the machine includes a second motor 63 mounted in the frame, a worm 65 connected to a drive shaft of the second motor 63 through a transmission shaft 64, and a worm wheel 66 engaged with the worm 65. A first gear 68 is mounted on a wheel shaft 67, and a second gear 69 is engaged with the first gear 68. A shaft 70 of the second gear 69 is eccentric from the center shaft 54 of the lever 55 in a vertical direction.
When the second motor 63 is driven and the first gear 68 rotates, the second gear 69 rotates. At this time, since the shaft 70 of the second gear 69 is vertically eccentric from the rotation shaft 54 of the lever 55, when the rotation shaft 54 moves to a position of the shaft 70, a fulcrum of swinging motion of the lever is shifted by an amount of deviation between the rotation shaft 54 and the shaft 70.
By changing the height of the fulcrum of the swinging motion of the lever, the height of the press plate when the cover is attached to the book block can be finely adjusted. Accordingly, even if thicknesses of book blocks are varied, good processing quality of cover attachment can be achieved.
When a book block is formed of quires, however, a top edge side and a bottom edge side of the book block generally have different thicknesses, and differing amounts of glue are applied to the top edge side and the bottom edge side of the book block in a glue application process. In this case, in the conventional machine for attachment of a cover to a book block, if the height of the press plate at cover attachment is adapted to the side of greater thickness, the processing quality of the cover attachment with respect to the side of smaller thickness becomes poor, and if the height is adapted to the side of smaller thickness, the processing quality of the cover attachment with respect to the side of greater thickness becomes poor, and therefore, there is a problem that good processing quality of the cover attachment can not be obtained.